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In situ studies of the thermal evolution of the structure and sorption properties of Mg-Al-CO3 layered double hydroxide

IN SITU STUDIES OF THE THERMAL EVOLUTION
OF THE STRUCTURE AND SORPTION PROPERTIES OF MG-AL-CO3 LAYERED DOUBLE HYDROXIDE
by
Yongman Kim
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMICAL ENGINEERING)
December 2006
Copyright 2006
Yongman Kim

Several in situ techniques have been used to investigate the thermal evolution of the structure of Mg-Al-CO3 layered double hydroxide under inert atmosphere. Based on the results of the study, a model was proposed to describe the structural evolution of the Mg-Al-CO3 LDH. The sorption characteristics and thermal reversibility of Mg-Al-CO3 LDH were also investigated with in situ techniques under both inert and reactive atmospheres. The experimental observations are shown to be consistent with the structural model proposed. The structure, sorption characteristics, and thermal reversibility of Mg-Al-CO3 LDH materials are important in their use for the high temperature applications.; Diffusivity constants and adsorption isotherms for carbon dioxide in Mg-Al-CO3 LDH were investigated by the gravimetric method at elevated temperatures. The experimental estimates of diffusivity constants and those obtained by molecular dynamic simulations are in good qualitative agreement. The experimental adsorption isotherms for CO2 in LDH have been studied with the Langmuir isotherm equation and various empirical adsorption isotherm equations. It is observed that the heterogeneity of the system and the interaction between CO2 and Mg-Al-CO3 LDH increases with temperature. Particle size effect on CO2 uptake and adsorption isotherm was also investigated. It was observed that both the amount of CO2 uptake and BET surface area increases as the particle size decreases. When the uptake amount was normalized with BET surface area, the uptake amount was fairly constant for all the ranges of particle sizes.; Various methods for the preparation of LDH membranes were studies, and the transport properties of prepared membranes were investigated. The values of separation factor were similar to Knudsen factor, and, to prepare perm-selective microporous LDH membranes, it is required to find an effective binder or a method for LDH crystals to intergrow each other.

IN SITU STUDIES OF THE THERMAL EVOLUTION
OF THE STRUCTURE AND SORPTION PROPERTIES OF MG-AL-CO3 LAYERED DOUBLE HYDROXIDE
by
Yongman Kim
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMICAL ENGINEERING)
December 2006
Copyright 2006
Yongman Kim